1. Field of the Invention
The present invention relates to transmitting, receiving, and automatic recording systems for broadcast programs with time and channel information contained in independent data in program signals.
2. Description of the Prior Art
Skyport scramble systems are designed in conformity with or on the basis of the conventional standard satellite broadcasting system. In the skyport scramble systems, video and audio signals to be transmitted are scrambled to provide privacy to the signal transmission service so that only subscribers who pay the charge for the service can receive the transmitted video and audio signals. Typically, the video signals are scrambled by line shuffling, and the audio signals are scrambled by adding quasi-random signals.
Various items of related information are also transmitted together with the video and audio signals in the skyport scramble systems. For example, the items of related information include program information as to transmitted programs, control information for forcibly turning off the descrambling capability of the decoder at a subscriber when the subscription contract expires, individual personal information such as subscriber's contract information and a work key to decipher information ciphers, and message information for additionally displaying information relative to the charged broadcasting service at a receiver.
As shown in FIG. 1 of the accompanying drawings, the items of related information are sent from a skyport administration center 1 to a plurality of scrambling devices 3a, 3b, . . . in various regions belonging to an earth station 2, and multiplexed with video and audio signals by the scrambling devices 3a, 3b, . . . Then, the multiplexed information is scrambled and transmitted from antennas 4a, 4b, . . . to a communication satellite 5, which then transmits the information to a subscriber's receiver 7. The information received by an antenna 6 is descrambled by the receiver 7, and displayed and reproduced by a television set or recorded in a video tape recorder 8 or the like.
The scrambled video and audio signals are descrambled from the related information into normal video and audio signals. To automatically record desired descrambled video and audio signals in the video tape recorder 8 or the like, the video tape recorder 8 should be programmed in advance to record the signals with suitable timer settings. However, no arrangements have been available for automatically recording scrambled programs in the skyport scramble system.